Fix labels widget update on hide dropdown on Ubuntu

What does this MR do and why?

Fixes labels widget on Ubuntu. Previously, clicking outside the dropdown didn't update labels.

Root cause: Due to the structure of labels widget, conditionally displaying the dropdown contents when SidebarEditableItem is in edit mode, the dropdown was dismounted by its parent before emitting setLabels event.

This fix ensures the events get emitted in the proper order.

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Before	After

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